Linear drive system for chemical mechanical polishing

ABSTRACT

A linear drive mechanism for chemical mechanical polishing includes a substrate carrier and support system which employs at least one linear motor to drive the substrate carrier through polishing motions. An additional driver for driving at least a portion of the carrier in directions perpendicular to the motions supplied by the linear motor(s) is also included. A clamping flexure is provided to selectively lock the substrate carrier in a vertical position. The substrate carrier, in one embodiment is mounted to a vertical driver via a column. The column is guided by spiral flexures to prevent motion in directions normal to vertical. An air mount is provided to support the majority of the mass of the substrate carrier, so that only a small force need be applied by the additional driver for movements in the vertical direction. Another, linear drive mechanism is described as using a “Sawyer motor” for both polishing motions as well as vertical force application.

This application is a divisional application of copending U.S. patentapplication Ser. No. 08/961,602, now U.S. Pat. No. 6,196,896 filed Oct.31, 1997 by Sommer, which is hereby incorporated by reference in itsentirety.

TECHNICAL FIELD

The present invention relates to chemical mechanical polishing ofsubstrates. More specifically, improved apparatuses and methods areprovided for linearly driving a substrate carrier to polish a substratesurface.

BACKGROUND ART

Chemical mechanical polishing to achieve the planarization of substratesurfaces, such as those of semiconductor wafers, flat panel displays,hard disks, etc. has become a very desirable method of processing. CMPtypically requires the mounting of a substrate into a head or carrierwhich is then urged against a polishing surface to effect polishing ofan exposed surface of the substrate. In the usual arrangements, both thecarrier and the polishing surface are rotated to apply a polishingaction.

For example, Kaanta et al., U.S. Pat. No. 5,036,630, discloses a methodof polishing a semiconductor wafer in which a wafer carrier is coupledto a spindle which is in turn driven by a motor to rotate the spindleand wafer carrier. The wafer carrier applies a load to the wafer andagainst a rotatable turntable assembly which includes a polishing tablethat is rotatably driven by a motor.

Hirose et al., U.S. Pat. No. 5,384,986, discloses a turntable with anabrasive cloth mounted thereon and a top ring, each of which areindependently rotated to perform polishing. The top ring drive shaft isrotatable about its own axis by a train of gears which are rotated by amotor.

Sandhu et al., U.S. Pat. No. 5,486,129, discloses a rotatable platenassembly which is coupled to a drive mechanism for rotation thereof. Ahead assembly supports and holds a face of a semiconductor wafer incontact with the platen assembly to polish the wafer face. A motor isconnected to the polishing head to rotate the polishing head. Individualregions of the wafer face are disclosed as having different polishingrates.

Shendon, U.S. Pat. Nos. 5,624,299 and 5,582,534, disclose a device forchemical mechanical polishing that includes a housing which isconfigured to provide orbital and rotational movement of a carrier. Agear arrangement is provided to rotationally drive the carrier while atthe same time sweeping the carrier arm through an orbital path. A motorand gear assembly may be connected to a platen to provide a rotationalpolishing surface against which the carrier moves.

The ideal substrate polishing process can be described by Preston'sequation: R=K_(p)*P*V, where R is the removal rate; Kp is a function ofconsumables (abrasive pad roughness and elasticity, surface chemistryand abrasion effects, and contact area); P is the applied pressurebetween the wafer and the abrasive pad; and V is the relative velocitybetween the wafer and the abrasive pad. As a result, the ideal CMPprocess should have constant cutting velocity over the entire wafersurface, constant pressure between the abrasive pad and wafer, andconstant abrasive pad roughness, elasticity, area and abrasion effects.In addition, control over the temperature and pH is critical and thedirection of the relative pad/wafer velocity should be randomlydistributed over the entire wafer surface.

Most of the current CMP machines, including those discussed above, failto produce constant velocity distribution over the entire substratesurface and thereby fail to achieve uniform material removal over theentire surface which is essential for a planar result. Consequently,wastage of significant portions of the substrates results, particularlyat the edges of the substrates.

Other relative motion arrangements have been attempted and described,but also fail to achieve constant velocity distribution over the entiresubstrate surface and thereby fail to achieve uniform material removalover the entire surface of the substrate.

Chisolm et al., U.S. Pat. No. 5,522,965, discloses a compact system forchemical mechanical polishing which employs a non-rotational platenhaving a polishing pad thereon, against which a wafer is rotated by arotating carrier. An ultrasonic energy is inputted to the platen in aneffort to enhance the polishing action.

Hirose et al., U.S. Pat. No. 5,643,056, discloses a revolving drum typepolishing apparatus A rotating drum having a polishing pad mounted onits outer peripheral surface is provided and is rotationally driven by amotor about its longitudinal axis. The drum is suspended above a waferto be polished by a column attached to a base. The wafer is seated on aY-table which is in turn mounted on a X-table which is fixed to thebase. The X and Y tables are able to oscillate in directionsperpendicular to one another, while the drum rotates against the surfaceof the wafer.

Lund, U.S. Pat. No. 5,643,044, discloses an orbiting wafer carrier whichis mechanically driven by an internal gear arrangement. An abrasive tapeis forcibly pressed against an exposed surface of the wafer, during theorbiting motion to effect polishing.

Parker et al., U.S. Pat. No. 5,599,423, discloses an apparatus forsimulating a chemical mechanical polishing system in an attempt tooptimize the same. A rotating platen is provided, against which apolishing pad forces a substrate. The force is applied to the polishingpad by a moveable tubular polishing arm which is preferably continuouslymoved linearly across the rotating substrate, from edge to center, untilthe polishing end point is attained.

In addition to the failure to develop an apparatus which removes aconsistent amount of material across the entire face of a substrateduring polishing, most of the current machines discussed require a largemass to be born by the carrier or head support due to the mechanicalarrangements which are provided for driving the carriers. This equatesto a large inertial mass which must be contended with when starting andstopping a polishing motion. For rotational carriers, this is not asignificant concern unless the rotational speed is to be frequentlyvaried. However, rotational carriers have the inherent drawback of notproviding a constant velocity distribution across the polishing surface.

Co-pending U.S. application Ser. No. 08/443,956, entitled “Method andApparatus for Chemical Mechanical Polishing, discloses apparatuses whichare capable of polishing a substrate while maintaining uniform averagevelocity between the substrate and an abrasive pad against which thesubstrate is polished. U.S. application Ser. No. 08/443,956 is herebyincorporated by reference thereto in its entirety.

For example, one embodiment disclosed in application Ser. No. 08/443,956includes a carrier which is driven in the Z-direction by a servo motorand lead screw. A cross member, post and linear slide must be supportedduring programmable movements by the servo motor and lead screw. Thecarrier is maintained substantially fixed in the X and Y directionsduring polishing. A table, which includes the polishing surface againstwhich the carrier polishes the substrate, is moved in the X and Ydirections during polishing. The table is mounted along a linear slideand is moveable therealong in the X direction by a lead screw and servomotor arrangement. For movement in the Y-direction, a plate is providedwhich supports the table and is in turn mounted to another slide formovement therealong in the Y direction. The plate is driven by a thirdservo motor and lead screw arrangement.

While the above discussed embodiment, as well as the other embodimentsdisclosed in the application, effectively maintain uniform averagevelocity between the substrate and the abrasive pad during polishing,they nevertheless require the movements of fairly significant inertialmasses to accomplish their functions. For example, in the embodimentdescribed above, the Y-direction servo motor and lead screw must drivethe combined weight of the plate and a portion of its slide, as well asthe table, the table slide and the servo motor and lead screw associatedwith the X-direction movement of the table. This puts a significantstrain on the servo motors, particularly the Y-direction servo in thisexample, which could lead to overheating and reduced service life of theservo and or lead screw. Even more significantly, the substantial massesinvolved limit the effective velocities at which the polishing patternscan be carried out.

Thus, there remains a need for systems with improved polishing velocitycapabilities, which can at the same time maintain uniform averagevelocity between a substrate and an abrasive pad against which thesubstrate is polished. An important objective is to reduce the inertialmass or masses to be moved, especially for devices that include startingand stopping motions or variations in patterns and/or velocities duringtheir operation. Another goal is to improve the performance of thedrivers which actually move the inertial masses through their polishingpatterns. More responsive drivers, i.e., drivers with improvedacceleration and velocity capabilities, are desirable.

Additionally, mechanical arrangements for driving a carrier can limitthe size of the polishing pattern that the apparatus is capable ofperforming. For example, the radius of the polishing path of theapparatus described in U.S. Pat. No. 5,643,053, is limited to thedistance between the drive shaft 56 and the second shaft 64 whichinterconnect the carrier with a motor. It would be desirable to have acapability to define a polishing pattern which would be limited only bythe useable surface of the polishing surface against which the carriertravels.

DISCLOSURE OF THE INVENTION

The present invention is directed to a linear drive mechanism forpolishing. Preferably, the present invention is directed to a drivemechanism for chemical mechanical polishing. The mechanism includes asubstrate carrier adapted to hold a substrate against a polishingsurface for polishing the substrate. The substrate carrier is mounted toa support structure which is adapted to guide linear movements of thesubstrate carrier along two substantially perpendicular directions.

At least one linear driver is associated with the support structure, anda driver is associated with said the substrate carrier to provide aforce to at least a portion of a face of the substrate carrier along athird direction substantially perpendicular to the two substantiallyperpendicular directions of polishing motion.

In a preferred embodiment, a base is provided upon which the supportstructure is movably mounted, and the support structure includes a firstsupport stage moveable, with respect to the base, in one of twosubstantially perpendicular polishing directions. A second support stageis mounted on the first support stage and is moveable, with respect tothe first support stage, in the other of the two substantiallyperpendicular directions.

Preferably, at least a first linear motor is mounted between the baseand the first support stage, and at least a second linear motor ismounted between the first support stage and the second support stage.More preferably, first and third linear motors are mounted between thebase and the first support stage, and second and fourth linear motorsare mounted between the first support stage and the second supportstage.

Additionally, at least one flex mount preferably mounts one of the firstand third linear motors to the first support stage, and at least oneflex mount preferably mounts one of the second and fourth linear motorsto the second support stage. A column preferably interconnects thesubstrate carrier and the driver, and transfers a driving force from thedriver to the substrate carrier, while at the same time restraining thesubstrate carrier from movements perpendicular to the direction of thedriving force.

A position sensor, preferably an encoder or a linearly variabledifferential transformer, is connected to the driver to sense a positionof the substrate carrier along the direction of driving force producedby the driver. The driver preferably comprises a voice coil motor and issupported by the support structure. Preferably, support arms are mountedto an exterior of the driver and supported by the support structure.Further, a support ring is preferably mounted to the support structureand connected to the support arms.

Further provided is a support apparatus interconnecting the substratecarrier with the support structure. The support apparatus includesdisplaceable support members connecting the substrate carrier with thesupport structure. A position of the substrate carrier along the thirddirection is adjustable by controlling a displacement of thedisplaceable support members. The displaceable support members alsopreferably support at least a portion of the mass of the driver, as wellas the mass of the substrate carrier.

At least one stabilizer preferably connects the column with the supportring, to allow vertical movements of the column with respect to saidsupport ring, and to substantially prevent movements of the column indirections perpendicular to vertical with respect to the support ring.Preferably, the stabilizer or stabilizers are spiral flexures.

A clamping flexure is preferably mounted to the support ring forreleasably clamping the column. When the column is clamped, it issubstantially immovable in the vertical direction, but when unclamped,the column is freely movable in the vertical direction.

In another preferred embodiment, the drive mechanism of the presentinvention includes a plate member and a plurality of magnets separatefrom the plate member and mounted to the substrate carrier. Force in thevertical direction is provided by an attractive force generated betweenthe plurality of magnets and the plate member. The plate member includesa plurality of projections extending in rows along two substantiallyperpendicular directions, and are selectively energizeable to produceforces between the projections which are energized and the magnets whichare aligned with the energized projections.

Further disclosed is a linear drive mechanism for polishing whichincludes a substrate carrier adapted to hold a substrate against apolishing surface for polishing the substrate, a support structuresupporting the substrate carrier and adapted to guide linear movementsof the substrate carrier along two substantially perpendiculardirections, and a driver associated with the substrate carrier andsupported by the support structure, to provide a driving force to thesubstrate carrier along a third direction substantially perpendicular tothe two substantially perpendicular directions.

Still further, a linear drive mechanism for polishing is disclosed toinclude a substrate carrier adapted to hold a substrate against apolishing surface for polishing the substrate, a plurality of magnetsmounted to the substrate carrier, and a plate member comprising aplurality of projections extending in rows along two substantiallyperpendicular directions. The projections are selectively energizeableto produce forces between the projections which are energized and themagnets which are aligned with the energized projections. In oneembodiment, the plurality of magnets are mounted peripherally of thesubstantially planar face of the substrate carrier. In anotherembodiment, the plurality of magnets are mounted in and substantiallyco-planar with the substantially planar face.

A polishing pad is positioned between the substrate carrier and theplate member, such that the substrate carrier is controllable to movethe substrate against the polishing pad and plate member to polish thesubstrate. Preferably, an interchange section is formed of a portion ofthe plate member, to extend beyond dimensions of the polishing pad, forinterchanging/inspecting substrates. The interchange section has anopening dimensioned slightly larger than the substrate but smaller thanthe substrate carrier.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an apparatus employing a preferredembodiment of a linear drive mechanism according to the presentinvention;

FIG. 2 is a perspective view of the X-Z portion of the linear drivemechanism shown in FIG. 1;

FIG. 3 is a plan view of the X-Z portion shown in FIG. 2, when viewedfrom the right in FIG. 2;

FIG. 4 is a perspective view of a spiral flexure incorporated into theZ-drive of the embodiment shown in FIG. 1;

FIG. 5 is a plan view of a clamping flexure employed in the embodimentshown in FIG. 1;

FIG. 6 is an end view of a preferred embodiment of a linear motor foruse in the present invention;

FIG. 7 is a top view of a fixed portion of the linear motor shown inFIG. 6;

FIG. 8 is a perspective general view of an alternative embodimentemploying open linear motors;

FIG. 9 is a view of the column which connects the Z-drive with thecarrier, and the support system therefor;

FIG. 10 is an exploded view of a flexure mount according to the presentinvention;

FIG. 11 is a perspective view of another embodiment of a linear drive amechanism according to the present invention;

FIG. 12 is a sectional view of an alternate arrangement of the polishingsurface shown in FIG. 11;

FIG. 13 is a sectional view of a carrier for use with the linear drivemechanism of FIG. 11;

FIG. 14 is a bottom view of the carrier shown in FIG. 13;

FIG. 15 is a sectional view of another carrier for use with the lineardrive mechanism of FIG. 11;

FIG. 16 is a bottom view of the carrier shown in FIG. 14; and

FIG. 17 is a sectional view of a variant of the carrier shown in FIG.13.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to FIG. 1, there is shown a perspective view of an apparatusemploying a preferred embodiment of a linear drive mechanism 100according to the present invention. A first support stage 120 isprovided for movement along one substantially linear direction, i.e.,the “X direction” indicated in FIG. 1. The first support stage 120 isalso referred to as the X-Z stage since it supports a substrate carrier(not shown) and a driver 240 for moving the substrate carrier in avertical or “Z” direction. The first support stage is shown in anenlarged, isolated, perspective view in FIG. 2.

A second support stage 170 is provided for substantially linear movementalong the “Y direction” indicated in FIG. 1. Since the second supportstage 170 supports the first support stage 120, the first support stage120 and everything it supports are also moved in the “Y” direction whenthe second support stage 170 is so moved. The second support stage 170is mounted upon supports 112 which rest upon base 110. Base 110 andsupports 112 are preferably formed of a very dense, stable material,most preferably granite. Alternatively, materials such as cast aluminum,MEEHNITE (a cast iron product) polystone (ground granite mixed with apolymer epoxy) or the like may be used

Underlying the second support stage 120 and the substrate carrier 102(see FIG. 3) of the apparatus 100 is a polishing surface (not shown)against which the substrate carrier presses and moves the substrate forpolishing the same. Preferably, the polishing surface is substantiallyimmobile, although a sheet of polishing material may be incrementally orslowly and continuously moved across the polishing surface between thepolishing surface and the substrate. However, a substantial polishingforce or motion is generally not provided by the polishing surface.Rather, the combined linear motions of the first and second supportstages 120, 170 can be programmed to form any desired polishing patternof the substrate carrier 102 against the polishing surface. The lineardrives of the apparatus are preferably computer controlled so that theoperator can program the X and Y motions to move the carrier 102 in aninfinite number of patterns. Additionally, because the carrier is notlimited by the length of a rotary arm, the programming of the movementsof the present device is not limited by any rotary arm length or radiusof a mechanical part, but only by the dimensions of the entire polishingsurface along which the carrier 102 may be moved by the linear drives.

In the preferred embodiment shown in FIG. 1, the second stage 170 ismounted to supports 112 via linear motors 130. Although linear motors130 are the preferred drivers for the second stage 170 in the presentinvention, the present invention is not to be limited to the use of onlylinear motors for purposes of driving. Alternative linear drivers, suchas screw drives driven by stepper motors or other motors may beemployed. A “Sawyer motor” arrangement could also be employed, asdescribed below.

The linear motors 130 each include a fixed portion 132 which comprises apair of opposing series of permanent magnets 134, and a movable coilportion 136 which is positioned between the opposing rows of magnets134. FIG. 6 is an end view illustrating the relationship between thefixed portion 132 and the movable coil portion 136.

The fixed portion 132 is formed to be substantially “U” shaped incross-section, to provide a space for receiving the coil portion 136between banks of opposing permanent magnets 134. The coil portion 136 isformed substantially as a “T” shape in cross section and is dimensionedto fit between the permanent magnets 134 without contacting them.Cooling lines 138 may optionally be provided to run the length of thecoil portion 136. Air or fluids may then be circulated through coolinglines 138 to prevent overheating and a resultant reduction inperformance of the linear motors. An electrical wire 139 also runs thelength of the coil portion 136 for energizing the linear motor. Thepreferred linear motors are supplied by Anorad Corporation, Hauppauge,N.Y., although alternative linear motors could be exchanged to performthe same functions. Additionally, although a pair of linear motors isillustrated for moving each of the above-identified stages, it is notedthat more than two linear motors, or even one linear motor could bearranged to provide the driving force needed for each of the respectivestages. Current linear motor specifications, as well as symmetry, preferthe arrangement shown in FIG. 1 over a single linear motor arrangement,and the use of more than two linear motors per stage adds to the cost ofthe device.

FIG. 7 shows a top view of part of a fixed portion 132 of a linear motor130 as employed in the present invention. The opposing banks ofpermanent magnets 134 run the entire length of the fixed portion 132.The polarity of the permanent magnets along each bank alternates witheach adjacent magnet, as shown in FIG. 7. The polarity of each permanentmagnet is also opposite that of the permanent magnet 134 on the oppositebank that opposes it.

The fixed portions 132 for driving the Y-stage 170 are mounted atopsupports 112. Each of supports 112 is finished with a substantially flatand planar surface 112 a which is oriented substantially horizontallylevel to support even controlled movements of both the Y-stage and theX-Z stage. Fixed portions 132 are mounted to surfaces 112 a by way ofbolts 132 a, screws, or other equivalent fixation elements. The fixedportions 132 are mounted to the surfaces 112 a as perfectly parallelwith each other as possible and aligned with the bases 112.

The Y-stage 170 is supported on the surfaces 112 a by way of rollerbearings (e.g., recirculation rollers) 174 which are mounted on surfaces112 a by any of the same connector elements mentioned with regard to themounting of the fixed portions above. The roller bearings 174 runparallel with the fixed portions 132. Preferably a roller bearing strip174 runs just inside of each of the fixed portions 132, as shown in FIG.1. Note that part of the fixed portion 132 shown on the right side ofthe apparatus of FIG. 1 has been cut away so as to more clearly show thepositioning of the roller bearings 174 with regard thereto. At least onebearing race 172 is mounted on the underside of the Y stage 170 forconnecting the Y-stage 170 with the respective supports 112 via rollerbearings 174. In this regard, each of the bearing races 172, only one ofwhich is shown in FIG. 1 is shaped so as to conform with the outercontour of the roller bearing 174 over which it rides. A better view ofthe detail of a bearing race 172 is shown in FIG. 3. Although the races172 are shown attached to the X-Z stage in FIG. 3, it is noted that thestructure of these races is the same as those provided for the Y-stageand discussed above.

The bearing races 172 include a hard substantially flat and planarsurface 172 a which is substantially horizontal when mounted andinterconnected with its respective roller bearing 174. Side ridges 172 bare provided for maintaining the position of the race with respect tothe roller bearings, in directions perpendicular to the direction inwhich the race is designed to move with respect to the roller bearings.

Either or both of the Y and X-Z stages may be provided with bearingraces that extend the entire length of the respective bearings overwhich they ride. More preferable, however, is to provide a pair of races172 to ride over each respective roller bearing strip 174. Thus, forexample, the left side of the Y-stage 170 shown in FIG. 1 is mounted totwo bearing races 174 (one of which is shown in phantom) at oppositeends of the left side of the stage 170 for movable support of the leftside of the stage 170. Of course, a similar arrangement would be mountedunder the right side of the stage 170 for movable support along theright side bearing strip 174.

Although the preferred embodiment shown in FIG. 1 uses roller bearingsfor movably supporting the respective stages to their supports forreducing friction as well as guiding the stages while they are driven bytheir respective linear motors, alternative reduced friction supportsmay be used. For example, air bearing surfaces may replace theabove-described roller bearing arrangements. An example of an airbearing arrangement is disclosed in U.S. Pat. No. 4,571,799, thedisclosure of which is hereby incorporated by reference in its entirety.

The coils 136 for movement of the Y-stage 170 are mounted to oppositesides of the Y-stage 170 by bolts, screws, welds or other alternativeequivalent for connecting the components. As shown in the detailed FIG.6, the coils are supported so that they touch neither the permanentmagnets 134 nor the bottom surface of the “U-shape” formed by the fixedportion 132. Thus, no sliding friction is generated by movement of thecoils 136 with respect to the fixed portions 132. Thus, the Y-stage 170in FIG. 1 is supported by the bearings 174 and races 172 configured asdiscussed above, and the Y-stage 170, in turn, supports the coils 136 intheir vertical position with respect to fixed portions 132.

It is further noted that while the “closed-type” linear motors describedabove with regard to FIGS. 1, 6 and 7 are the preferred type of linearmotors for use in the present application, that “open-type” linearmotors, although less preferable, could also be employed in place of the“closed-type” motors. An example of open-type linear motors 130′ isshown in FIG. 8. In contrast to the closed-type motors, the open-typemotors have a single strip of alternating polarity permanent magnets134′ which interact with a coil 136′ that is parallelly positioned tothe magnets 134′. Because of the external magnetic fields generated bythe open-type motor, the closed-type linear motors are preferred in thepresent invention.

Referring back to FIG. 1, first support stage 120 is.shown mounted ontop of second support stage 170. The mounting of first support stage 120to second support stage 170 is analogous to the mounting of the secondsupport stage 170 to supports 112, as discussed above. However, thefirst support stage 120 is, of course, mounted transverse to the secondsupport stage 170, to enable movement of the first support stage 120 inthe X direction shown in FIG. 1.

Thus, bearing strips 174 are mounted along the top substantially flatand planar surfaces 170 a of the second support stage 170 that areoriented perpendicularly to the orientation of the linear motors 130that drive the second support stage 170. The surfaces 170 a aresubstantially level and horizontal upon mounting the second supportstage 170 on the supports 112. A pair of fixed portions, 132 includingfixed magnets 134 as described above, are mounted along the outsideedges of surfaces 170 a, substantially parallel to one another as wellas to the roller bearings 174. A pair of coils 136 are mounted toopposite sides of the bottom surface of first stage 120 as shown in FIG.2. The coils 136 may be bolted, screwed, or otherwise fixed to the stage120. The coils are positioned so as to fit within the fixed portionswithout touching the fixed portions, as shown in FIG. 6 and describedabove with regard to the linear motors for the second support stage. Thefixed portions 132 are mounted at a height with respect to the firstsupport 120, that prevents the coils 136 from bottoming out on theU-shape surface within the respective fixed portions 132 when the firststage 120 is supported by the roller bearings 174 and bearing races 172.

Referring to FIG. 3, the bearing race 172 shown on the left side of theFIGURE, as well as the bearing race 172 located directly behind thatbearing in the FIGURE (not shown) are fixedly mounted to the bottom ofsupport stage 120. The fixed bearing races 172 on the left side of FIG.3 are aligned parallel to the roller bearings 174 which they will fitand roll over, and parallel to the coil 136. The bearing race 172 on theright side of FIG. 3, as well as the bearing race 172 located directlybehind that bearing in the FIGURE (not shown) are flexibly mounted tothe first support via flexure mountings 176 (FIG. 2).

As shown in an exploded view in FIG. 10, each flexure mounting 176includes a rigid base plate 176 a that is fixed to the support structure(first or second support structure). A thin metal flexure (flexibleplate) 176 b is interconnected between base plate 176 a and mountingplate 176 c by brackets 176 d and bolts, screws or other equivalentconnectors (not shown). The bearing race is mounted to mounting plate176 c using similar connectors. With this type of mounting, the bearingrace is free to flex and twist within a limited range made possible bythe flexibility of flexible plate 176 b, and in the example described iscapable of a limited amount of twisting and flexing relative to thesupport 120 and the opposite bearing/race arrangement (left side of FIG.3). This flexibility allows the first support to smoothly move along thesupport pathways defined by the parallel bearing and race arrangements,even when a slight deviation from a parallel positioning occurs, eitherthrough temperature variations, design tolerances, slight misalignmentof the bearings from perfect parallel positioning, etc. Similarly, oneset of bearing races is provided with this flexibility on the secondsupport stage to provide the same benefits.

Support stages 120 and 170 are preferably formed of Aluminum or otherlight weight metal in an effort to keep the inertial mass to be moved toa minimum The first stage 120 is provided with reinforcing beams 122 ofaluminum to help maintain planarity of the support surface whilesupporting the load of the substrate carrier and associated componentsdescribed below.

As indicated previously and shown in FIG. 3, the substrate carrier 102is supported by the X-Z stage 120. The substrate carrier 102 is mountedto a column 220 which is supported for vertical movement (i.e., movementin the “Z direction” as shown in FIG. 3). The upper end of the column220 is mounted to a driver 240 which is adapted to provide a drivingforce in the Z-direction. Preferably, the drive 240 is a voice coilmotor, but other equivalent, drivers could be substituted. In general,the travel distance in the Z-direction is not required to be very large,as the driver is used mainly to preset a vertical position of thesubstrate carrier 102 against the polishing surface, with a desiredamount of force. A position sensor 250, preferably an encoder orlinearly variable differential transformer (LVDT) is provided to sensethe vertical positioning of extendible portion of the voice coil motor240 and consequently the substrate carrier 102.

The immovable part of the driver 240 and the position sensor 250 aresupported by the first support 120 through support arms 252 whichinterconnect the driver 240 housing with support ring 254. Support ring254 is mounted to first support 120 by bolts, screws or other equivalentconnectors. Support ring 254 and support arms 252 are preferably made ofaluminum or other lightweight, structurally rigid metal. Although threesupport arms 252 are shown supporting the driver 240 in FIG. 3, theinvention is not limited to this number as two, four or more supportarms could be employed. However, three is a preferable numberconsidering the rigidity it provides with a minimum of weight. Thesupport ring 254 is provided with a number of supporting columns 256 anda number of cutout areas 258 in the interests of weight reduction.

The weight of the substrate carrier 102 and column 220, as well as themoveable portion of the driver 240 are born by an arrangement ofadjustable air cylinders 260 mounted on opposite sides of the column220. As shown in FIG. 1, the lower ends of cylinders 260 are bolted orotherwise connected to the first support 120. The extendible shaft 261of each cylinder 260 is mounted, preferably by a ball and socket orequivalent joint 266, to a horizontal support arm 262. Horizontalsupport arms 262 are threaded or otherwise affixed into column 220.

Air input lines 268 are provided on each of the air cylinders 260 sothat the internal pressure of the cylinders 260 may be controlled tocontrol the amount of extension or height of the extendible shafts 261.Thus, air cylinders can be manually or automatically (e.g., bymicroprocessor) controlled to adjust a homing position or “setpoint” ofthe vertical height of the substrate carrier.

FIG. 9 is an isolated view of the substrate carrier 102, column 220,driver 240, position sensor 250 and the supporting structure forsupporting the weight of the substrate carrier, column and movingportion of the driver for transfer to the first supporting stage 120.The air cylinders 260 are schematically shown as being mounted to asupport surface which signifies support stage 120. As can be seen moreclearly in FIG. 9, the column 220 extends from driver 240 all the way tothe connection with substrate carrier 102 and thus supports the load ofthe substrate carrier 102 and vertically moves with the substratecarrier 102.

Accordingly, a starting or setpoint position may be established byde-energizing the driver 240 so that its movable portion 240 a may befreely adjusted by external forces. Next, the air pressure within aircylinders 260 is adjusted to raise or lower the horizontal support bars262 as desired to establish the starting height of substrate carrier102. Once the setpoint is established, only a small force need begenerated by the driver 240 to incrementally adjust the verticalposition of the substrate carrier, since the resistance of the aircylinders is roughly equilibrated with the mass that they aresupporting. The result is that the carrier 102 and associated linkageappear to “float” on the air cylinder support and are easily moved bythe driver 240.

Although only two air cylinders 260 are shown in the FIGURES herein, itis noted that a pair of cylinders may be mounted at each end of thesupporting arms, depending upon the weight of the components that needto be supported and the performance specifications of the air cylinders.It is even contemplated that three or some other number of cylindersmight be provided at each end of the support arms and that the inventionshould not be limited to the number of air cylinders shown in theFIGURES. The preferred air cylinders are Airpel Anti-Stiction AirCylinder by Airpot Corporation of Norwalk, Conn.

In order to prevent movements of the column 220 in directions other thanthe Z direction, the column 220 is mounted to the support ring with apair of spiral flexures 280. One spiral flexure 280 is mounted at aheight that is approximately equal to the top height of the support ring254 and the other is mounted at about the same height as the bottom ofthe support ring 254, as shown in FIG. 1. FIG. 4 shows a spiral flexure280 in better detail. The spiral flexure is formed of metal, preferablya sheet of spring steel or other thin sheet of relatively rigid metal.Boundary portions 282 and 284 are provided along the inner and outercircumferences of the spiral flexure 280 to improve failure resistanceat the points of connection. Mounting holes 286 are used to mount thespiral flexure 280 to the column 220 using bolts or other equivalentconnectors, while the mounting holes 288 are provided for connecting thespiral flexure 280 to the support ring 254 in like manner.

Spiral slots 290 begin near the border of the boundary portion 284 andspiral radially inwardly to end near the border of the boundary portion282. The slots 290 are preferably radiused at each end 292 to preventstress concentration. The spiral slots allow deformation of the boundaryportion 282 with respect to the boundary portion 284 in directionsperpendicular to the plane of the spiral flexure 280, but substantiallyprevent any radial movement of the boundary portion 282 with regard tothe boundary portion 284. When assembled, the spiral flexures 280effectively restrict movements of the column 220, moveable portion ofthe driver 240 a and substrate carrier 102 to the Z direction shown inFIG. 3.

After establishing the setpoint or starting position of the substratecarrier 102, the driver 240 is actuated to apply the substrate carrier102 against the polishing surface or to a desired position either aboveor below the setpoint. Upon achieving the desired position, it is thendesirable to maintain that position, at least during polishing. Becausethe driver 240 is designed to be lightweight and is not designed towithstand the forces that might be transferred to it during polishing, amechanical arrangement is provided to maintain the desired positioningthat is initially set by the driver 240. Preferably, a clamping flexure300 is provided to fix the vertical position of the column 220 withrespect to the first support stage 120.

The clamping flexure is supported by and mounted to the support columnsof the support ring 254 along the mounting portion 302. A biasingportion 306 of the clamping flexure prebiases the clamping portion 304to a clamped position around the column 220. Bellville washers or otherbiasing members are provided around a bolt 310 to maintain a biasingpressure which effectively tends to squeeze arms 306 a,306 a toward oneanother so as to apply the clamping force. When it is desired to movethe vertical position of the substrate carrier, to set the setpoint,remove a substrate, or for whatever purpose, the clamping flexure mustbe released from the clamping position to allow the free verticalmovement of the column 220.

To release the clamping force, an air cylinder 312 (or other actuator,e.g., a solenoid, hydraulic piston, etc.) is provided. Upon increasingthe air pressure within air cylinder 312, piston 314 is biased tocompress or press together the Bellville washers 308. thereby releasingthe biasing pressure upon arms 306 a,306 a and freeing the column 220for vertical movement. When a desired vertical position of the substratecarrier has been reached, the air pressure is released from or reducedwithin the air cylinder 312, allowing the Bellville washers to drive thepiston 314 away and to reapply a clamping force through the arms 306a,306 a.

FIG. 11 shows another embodiment of a linear drive mechanism 400 forchemical mechanical polishing according to the present invention. Asubstrate carrier 402 is provided to hold a substrate (not shown)against a polishing surface 404, and to move the substrate in an X-Yplane according to predetermined polishing pattern to accomplishpolishing of the substrate. A support structure upon which the carrier402 is mounted includes a polishing plate 406 which, together with thepolishing pad 405 form the polishing surface 404. Additionally, anelastic, flexible pad 401 may be positioned between polishing plate 406and polishing pad 405, as shown in FIG. 12. Preferably, the flexible padcomprises a polycarbonate layer on top of a polyurethane layer, althoughother equivalent compositions may be used for the flexible pad. Theflexible pad 405 is mounted to the polishing plate 406, to help maintainuniformity of the polishing surface during polishing.

The polishing plate 406 is preferably a plate of ferromagnetic materialsuch as iron or steel having a plurality of substantially equally spacedparallel grooves 407 cut into the surface thereof along one axialdirection of the plate (the “Y” direction shown in FIG. 11), and aplurality of grooves 408 cut into the surface of the plate 406perpendicular to grooves 407. The spacing between grooves 408 ispreferably substantially equal to the spacing between grooves 407.Between the grooves 407 and 408 are formed projections or spikes 409,which are formed of the ferromagnetic material and project to thesurface of the polishing plate 406. The grooves 407 and 408 arepreferably filled with a non-magnetic material such as a plastic, resinor equivalent to form a smooth an planar surface with the projections409 while maintaining a magnetic separation between the projections 409.Alternatively, the grooves may be left open with air separating themagnetic projections 409 although this arrangement is not as preferable.

The entire polishing plate 406 is grooved as described above, althoughonly a portion of the grooving can be seen in FIG. 11 since thepolishing pad 405 (and optionally, elastic, flexible pad 401) covers themajority of the polishing plate 406. The polishing pad 405 preferablycomprises a thin film having an abrasive thereon. The thin film iscontained in a magazine which includes a take up roller 410 and deliveryroller 412 on opposite ends of the polishing plate 406. The take uproller is preferably motor driven to advance the polishing pad 405 andthe delivery roller 412 is preferably provided with a motor, brake orother means of providing a resistive force R in the direction oppositethe direction of advancement so as to be able to control an amount oftension that is applied to the polishing pad 405 between the rollers410,412. The preferred magazine and film are disclosed in copendingapplication Ser. No. 08/833,278, entitled “Polishing Media Magazine forImproved Polishing”, the entirety of which is hereby expresslyincorporated by reference herein. Alternatively, the polishing pad maybe a fixed abrasive containing layer mounted on the polishing plate 406,with or without a flexible pad 401 mounted therebetween, or otherequivalent. The flexible pad 401 is preferably an elastic, flexible padcomprising a polycarbonate layer on top of a polyurethane layer,although other equivalent compositions may be used.

The carrier 402 preferably includes four sets of magnets 420,422,424 and426 mounted therein (see FIG. 14) with the pole faces of the magnetsbeing approximately flush with the platen 431 of the carrier, so thatthey can be positioned closely adjacent the polishing surface 404. Eachpole face has one or more ridges of magnetic material and preferably isprovided with a plurality of ridges of the same width and spacing as theprojections 409 of the magnetic material in the polishing plate 406. Adetailed description of the operation and functioning of the magnets420,422,424 and 426 with respect to the projections 409 can be had byreferring to U.S. Pat. No. 3,376,578, the entirety of which is herebyincorporated by reference herein.

Referring back to FIG. 11, the functioning and movement of the carrier402 with regard to the polishing surface is the same in the X directionas it is in the Y direction, and both directions may be simultaneouslycontrolled so as to produce any desired polishing pattern of the carrier402 along the polishing surface 406. Regardless of the polishingpattern, however, the magnets 420,424, and 422,426, remain parallel withthe grooves 407 and 408, respectively. Thus, the carrier 402 maintainsuniform average velocity between all points on the polishing surface ofthe substrate and the polishing surface 404 at all times along anyselected polishing pattern.

Magnetic coupling is utilized between the magnets 420,422,424 ad 426 andthe polishing plate 406 for moving and positioning the carrier 402 alongthe polishing surface. Additionally, the attractive force betweenmagnets 420,422,424 and 426 and the polishing plate 406 provides a forceF in the Z direction (see FIG. 13) which is required to effectivelypolish the surface of the substrate. The force F can be varied andcontrolled by controlling the distance between the magnets (420, 422,424 and 426) and the polishing plate 406. Preferably, the distancebetween the magnets and polishing plate is controlled by varying thevertical position of a ring assembly described hereafter.

As shown in FIG. 13, the carrier 402 is further provided with a ringassembly which functions to retain the substrate in juxtaposition withthe platen 431 surface during polishing. The ring assembly includesrings 428, 446 and 448. The vertical position of the ring assembly withrespect to the platen 431 surface can be accurately controlled andvaried as the need arises. In addition to controlling the amount of downforce F (i.e., force in the Z direction), applied to the substrateduring polishing, the pressure applied by ring 446 against the abrasivesurface during polishing may be accurately controlled, and acts tominimize any standing waves of chemical slurry (or of the abrasive pad)that tend to be generated by the motion of the carrier during polishing.

The vertical position of the ring assembly 428,446,448 is preferablycontrolled by the positioning of air cylinders circumferentially aroundthe carrier between ring 428 and the top plate 411 of the carrier.Cavities 430 a are formed in a channel 430 circumferentially about topplate 411 and are preferably equidistantly circumferentially placed. Ina preferred embodiment, six cavities 430 a are formed in the channel430, but more or fewer cavities may be used. Equidistant circumferentialplacement of the cavities is preferred, since the cavities define thelocations from which pressure is exerted against ring 428, and it isdesirable to have the ability to apply a substantially constant forcearound the circumference of the ring 428.

A diaphragm 432 is mounted in each of cavities 430 a, and a cylinderring 434 is fixed to the bottom side of the top plate 411 (preferably byscrews or bolts or other equivalent fixation elements) to seal eachdiaphragm 432 in an airtight manner between each respective cylinderring 434 and the top plate 411. Thus, a sealed cavity is formed betweeneach diaphragm 432 and cavity 430 a. On the top side of top plate 411,opposite each cavity 430 a location, a port 436 a is formed. A pressurefitting 436 is fixed within each port 436 a, preferably by matingthreads. However, other equivalent methods of fixation may be employed.Also, various known types of thread sealant may be applied between themating threads of the pressure fitting 436 and port 436 a to improve theseal therebetween.

Pressure fittings 436 are connectable to tubing (not shown) forapplication of pressure/vacuum to control the pressure within thecavities 430 a. Increase of pressure within cavities 430 a causes adistention of diaphragms 432. Pistons 438 are abutted against diaphragms432 in cavities 430 a. Ring 428 is mounted to pistons 438, preferably byscrews 440 although alternative, equivalent fixation elements may beemployed. Screws 440 are countersunk with respect to the surface of ring428 so as not to protrude beyond the under surface of ring 428.

Flexure ring 442 is mounted to the top plate 411 via screws 444 or otherequivalent fixation elements, and is also mounted between ring 428 andpistons 438 via screws 440. Flexure ring 442 is preferably made of anonmagnetic metal or composite having stiff yet resilient properties.Flexure ring 442 functions to connect ring 428 to the top plate 411,while allowing some vertical movement of ring 428 with respect to thetop plate 411. Thus, when pressure is applied to cavities 430 a,diaphragms 432 distend to move pistons 438, and hence, ring 428, in avertical direction away from the top plate 110. Assuming the ring 146 isabutted against the polishing surface 404 at the time of pressurizingthe cavities 430 a, this effectively moves the magnets 420,422,424,426away from the polishing plate 406 each by an equal distance, effectivelyreducing the attractive force between the magnets and the polishingplate and ultimately reducing the force F of the carrier against thewafer and polishing surface.

Upon release of the pressure within cavities 430 a, potential energystored in the flexure element is converted to kinetic energy and, aidedby the attractive forces between the magnets and the polishing plate,acts to retract ring 428 and pistons 438 in a vertical direction towardthe top plate 411, thereby reducing the distance between the magnets andthe polishing plate and increasing the force F.

Retainer 446 is preferably made of a polyacetyl copolymer such as DELRIN(or other substantially equivalent linear acetal resin, or polyphenkoertalyte). A clamp ring 448 and screws or other equivalent attachmentdevices 450 are preferably made of aluminum or other nonmagnetic metalor composite suitable for use in the production of the substrate carrieraccording to the present invention as described above. Clamp ring 448 issufficiently rigid to ensure an immovable fixation of the retainer 446with ring 428.

Retainer 446 is designed to be durable and tough, but is expected towear during operation. Retainer 446 is substantially electricallynonconductive to avoid any potential interference with thesemiconductive properties of the wafer (e.g., wear of a metal retainercould introduce metal particles into the wafer), and nonmagnetic so asnot to interfere with the operation of the magnets 420,422,424,426 withthe polishing plate 406. Retainer 446 may be readily replaced aftersufficient wear has occurred.

Although the control of the vertical position of the ring assembly hasbeen specifically described with regard to the diaphragm/piston assemblyset forth above, it is to be noted that other pneumatic, hydraulic ormotor driven arrangements could be substituted to effectively controlthe vertical position of the ring assembly with respect to the substratecarrier, so as to control the downward force F of the platen 431 uponthe substrate.

Still further, additional and independent magnet drivers 490 may beprovided to adjust the vertical position of magnets 420,422,424, and 426with respect to the carrier 402′ as well as the ring assembly, as shownin the variant of FIG. 17. In this arrangement, a step motor 491 orother controllable electrical motor is mounted to the top of the carrier402′ via mount 492 adjacent each end of each magnet 420,422,424 and 426.Thus, a pair of magnet drivers 490 are preferably provided for each ofmagnets 420,422,424 and 426. Each motor 491 is connected to an end ofone of the magnets via a screw drive 494. Accordingly, the motors can becontrolled for synchronous movement to maintain the magnets parallel toeach other and to the polishing surface 406. Thus, the downward “Zforce” can be controlled independently of the vertical positioning ofthe ring assembly with respect to the carrier 402′.

The carrier is further preferably provided with a chamber 413 which maybe pressurized/evacuated to alter the shape of the platen 431, apressure fitting 415 is provided for accessing the chamber 413 to supplypressurized air or other gas or fluid to vary the surface conformationof the platen 431, and ultimately vary the pressures applied todifferent portions of the surface of the substrate to be polished, asneeded. For example, the pressure in chamber 413 can be increased tocause platen 413 to bow outwardly so as to apply additional pressure tothe central portion of a substrate, thereby increasing the rate ofpolishing in the central portion. A pressure gauge 417 is preferablyprovided to interface with the chamber 413 so as to provide feedback forcontrolling the internal pressure of the chamber, either manually orautomatically.

Optionally, a second chamber 421 or port may be provided for applyingair pressure or vacuum directly to the substrate through the platen, asshown at port 421. One or more pressure fittings 419 are provided forseparate control of the port 421, to either hold the substrate againstthe platen 431 using a vacuum. or to disengage the substrate from theplaten 431 with air pressure.

FIG. 15 shows an alternative embodiment of a carrier 502 for use withthe apparatus shown in FIG. 11, whereby the carrier 502 would besubstituted for the carrier 402 shown in FIG. 11. The carrier 502preferably includes four sets of magnets 520,522,524 and 526 (see FIG.16) which are analogous to the magnets 420,422,424 and 426 in theembodiment shown in FIG. 13. However, unlike the embodiment shown inFIG. 13, the magnets 520,522,524 and 526 are mounted in the platen 531with the pole faces of the magnets being approximately flush with theplaten 531 of the carrier 502, so that they form a planar surface withthe surface of the platen 531 as shown in FIG. 15. The magnets may bemounted in the platen 531 by bolting, screwing, epoxy, or otherequivalent fixation means which will securely hold the magnets flushwith the platen even during slight flexing of the platen. Each pole facehas one or more ridges of magnetic material and preferably is providedwith a plurality of ridges of the same width and spacing as theprojections 409 of the magnetic material in the polishing plate 406.

Thus, in this embodiment, the magnets 520,522,524 and 526 actuallycontact the back side of the substrate during polishing. Nevertheless, adownward or “E” direction force is still provided by the attractiveforces between the magnets 520,522,524 and 526 with the polishing plate406, as the magnetic fields pass through the substrate.

The carrier 502 is further provided with a ring assembly which functionsto retain the substrate in juxtaposition with the platen 531 surfaceduring polishing, just as described with the embodiment of FIG. 13.Likewise, the vertical position of the ring assembly with respect to theplaten 531 surface can be accurately controlled and varied as the needarises. In addition to controlling the amount of down force F (i.e.,force in the Z direction), applied to the substrate during polishing,the pressure applied by ring 446 against the abrasive surface duringpolishing may be accurately controlled, and acts to minimize anystanding waves of chemical slurry (or of the abrasive pad) that tend tobe generated by the motion of the carrier during polishing.

In order to provide for more efficient interchange of substrates to bepolished, the polishing plate 406 is preferably provided with aninterchange section 403 which extends beyond the boundaries of thepolishing pad 405. Although the interchange section is shown asextending from the side of the polishing pad 405, the placement of thesame is not to be so limited as the interchange section 403 may be placeanywhere along the boundary of the polishing pad. The interchangesection 403 is shown in FIG. 11 to be formed substantially in a “U”shape which has been found to be the most efficient arrangement for itsfunction. However, the section 403 may be formed in otherconfigurations, so long as an opening 403′ is provided which isdimensioned to allow a substrate to pass therethrough while at the sametime supporting at least a pair of outer edges of the carrier.

In practice, after completion of polishing of the substrate with theapparatus shown in FIG. 11, or at any time when the operator desires tovisually inspect the polished surface of the substrate, the carrier 402can be controlled to move off the polishing pad and onto the interchangesection where the Y-direction (in this example) magnets would stillfunction to move the carrier 402. Upon fully positioning the carrier 402on the interchange section 403, the substrate would then be free to dropthough the opening 403′ for receipt and inspection by the operator.

Additionally or alternatively, the magnet drivers 490 may be designed toposition the magnets low enough, with respect to the platen, to allowthe operator to freely slide the substrate out from beneath the platenand ring assembly and to slide another substrate into position to bepolished.

Although there have been described above specific arrangements of lineardrive devices for polishing, with a limited selected number ofalternative embodiments in accordance with the invention for the purposeof illustrating the manner in which the invention may be used toadvantage, it will be appreciated that the invention is not limitedthereto. Accordingly, any and all modifications, variations orequivalent arrangements which may occur to those skilled in the artshould be considered to be within the scope of the invention as setforth in the claims which follow.

What is claimed is:
 1. A linear drive mechanism for polishing,comprising: a substrate carrier adapted to hold a substrate against apolishing surface for polishing the substrate; a plurality of magnetsmounted to said substrate carrier, wherein the plurality of magnets arearranged in rows defining a slot therebetween; and a plate membercomprising a plurality of projections extending in rows along twosubstantially perpendicular directions, the projections being at leastpartially disposed in the slot and selectively energizeable to produceforces between said projections which are energized and magnets,selected from said plurality of magnets, which are aligned with saidenergized projections.
 2. The linear drive system of claim 1, whereinthe magnets alternate polarity along each side of the row and across therow.
 3. A linear drive mechanism for polishing, comprising: a substratecarrier adapted to hold a substrate against a polishing surface forpolishing the substrate; a plurality of magnets mounted to saidsubstrate carrier, wherein the plurality of magnets are grouped into atleast a first group of magnets and a second group of magnets, the secondgroup of magnets having an orientation perpendicular to the first groupof magnets; and a plate member comprising a plurality of projectionsextending in rows along two substantially perpendicular directions, saidprojections being selectively energizeable to produce forces betweensaid projections which are energized and magnets, selected from saidplurality of magnets, which are aligned with said energized projections.4. The linear drive system of claim 3 further comprising a first stagesupporting the substrate carrier and having some of the projectionscoupled thereto.
 5. The linear drive system of claim 4 furthercomprising a second stage having the first group of magnets coupledthereto.
 6. The linear drive system of claim 5, wherein the second stagecomprises some projections coupled thereto and interfacing with thesecond set of magnets.
 7. The linear drive system of claim 6, whereinthe second set of magnets are disposed on two supports extending betweenthe polishing surface and the carrier.
 8. The linear drive system ofclaim 5, wherein the first stage is movably coupled to the second stage.9. A linear drive mechanism for polishing, comprising: a substratecarrier adapted to hold a substrate against a polishing surface forpolishing the substrate; a plurality of magnets mounted to saidsubstrate carrier; and a plate member comprising a plurality ofprojections extending in rows along two substantially perpendiculardirections, said projections being selectively energizeable to produceforces between said projections which are energized and magnets,selected from said plurality of magnets, which are aligned with saidenergized projections; a first stage supporting the substrate carrier;and a second stage supporting the first stage.
 10. The linear drivesystem of claim 9 further comprising one or more bearings disposedbetween the first and second stages.
 11. The linear drive system ofclaim 10, wherein the bearing further comprises: a rail coupled to thesecond stages; a guide slidably mounted to the rail; and, a flexurecoupling the guide to the first stage.
 12. A linear drive mechanism forpolishing, comprising: a substrate carrier adapted to hold a substrateagainst a polishing surface for polishing the substrate; a plurality ofmagnets mounted to said substrate carrier; a plate member comprising aplurality of projections extending in rows along two substantiallyperpendicular directions, said projections being selectivelyenergizeable to produce forces between said projections which areenergized and magnets, selected from said plurality of magnets, whichare aligned with said energized projections; a column coupled to thecarrier; and a driver adapted to transfer a force through the column tourge the carrier towards the polishing surface.
 13. The linear drivemechanism of claim 1, wherein said substrate comprises a substantiallyplanar face adapted to apply pressure against the substrate duringpolishing, and wherein said plurality of magnets are mountedperipherally of said substantially planar face.
 14. The linear drivemechanism of claim 1, wherein said substrate carrier comprises asubstantially planar face adapted to apply pressure against thesubstrate during polishing, and wherein said plurality of magnets aremounted in and substantially co-planar with said substantially planarface.
 15. The linear drive mechanism of claim 1, further comprising adriver for adjusting a distance of said plurality of magnets from saidplate member.
 16. The linear drive mechanism of claim 1, furthercomprising a polishing pad positioned between said substrate carrier andsaid plate member, wherein said substrate carrier is controllable tomove the substrate against said polishing pad and said plate member topolish the substrate.
 17. The linear drive mechanism of claim 1, furthercomprising an interchange section formed of a portion of said platemember that extends beyond dimensions of said polishing pad, saidinterchange section having an opening dimensioned slightly larger thanthe substrate but smaller than said substrate carrier.
 18. The lineardrive mechanism of claim 3, wherein said substrate carrier comprises asubstantially planar face adapted to apply pressure against thesubstrate during polishing, and wherein said plurality of magnets aremounted peripherally of said substantially planar face.
 19. The lineardrive mechanism of claim 3, wherein said substrate carrier comprises asubstantially planar face adapted to apply pressure against thesubstrate during polishing, and wherein said plurality of magnets aremounted in and substantially co-planar with said substantially planarface.
 20. The linear drive mechanism of claim 3, further comprising adriver for adjusting a distance of said plurality of magnets from saidplate member.